1. Field of the Invention
The present invention relates to an exhaust apparatus for discharging an exhaust gas of an engine and air having provided cooling for an engine room, to an outside of the engine room, in a construction machine such as a hydraulic excavator equipped with the engine and the engine room.
2. Description of the Related Art
A background art of the present invention is described by taking a hydraulic excavator as an example.
A general hydraulic excavator includes a crawler-type lower crawling body, an upper slewing body slewably mounted around an axis perpendicular to a ground surface on the lower crawling body, and a working attachment attached to the upper slewing body. At a rear end part of the upper slewing body is provided an engine room, in which a plurality of devices such as an engine, a cooling fan, a muffler, and a heat exchanger are disposed.
This type of a hydraulic excavator may be provided with an apparatus for discharging exhaust gas from the engine and exhaust wind which is air having been sucked into the engine room by the cooling fan and having cooled the heat exchanger and the like, to an outside of the engine room; as such an apparatus, there have been known one disclosed in Japanese Patent Application Laid-Open No. H3-229907 or Japanese Patent Application Laid-Open No. 2013-024078. The apparatus described in each of the documents have a duct and an exhaust gas pipe. The duct is provided in the engine room and has a cylindrical shape opened at upper and lower opposite sides. The exhaust gas pipe has a tip end part inserted into the duct to mix the exhaust gas with the exhaust wind in the duct. This allows the exhaust gas whose temperature has been decreased to be discharged outward and enables the reduction in the noise generated by operation in the duct to be expected.
The insertion of the tip end part of the exhaust gas pipe into the duct, however, involves an increase in a required length of the exhaust gas pipe as compared with a case of piping the exhaust gas pipe to an outside of the engine room in a shortest distance independently of the duct. The increase in the pipe length basically involves increased vibration of the exhaust gas pipe.
In addition, the above exhaust gas pipe, being joined to a muffler connected to the engine, can be vibrated integrally with the engine as a part of an engine vibration system; therefore, when resonance occurs, it may make the vibration of the entire exhaust gas pipe be greater to thereby break the exhaust gas pipe. Problems in durability can be thus generated.
Besides, the increase in the required length of the exhaust gas pipe involves a difficulty of securing sufficient strength of the exhaust gas pipe.